User manual

IEC61131 User and Reference Manual
April 22, 2008
492
The Maximum Fragment Length is maximum size of a single response fragment that the RTU will
send. If the complete response message is too large to fit within a single fragment, then the
SCADAPack controller will send the response in multiple fragments. Valid values are between 100
and 2048 bytes.
This parameter is adjustable to allow for interoperability with simple DNP3 devices that require
smaller application layer fragments. Devices with limited memory may restrict the application layer
fragment size to as low as 249 bytes.
Note: The Maximum Fragment Length parameter applies to responses from read
commands only. It does not affect unsolicited responses.
The Retries entry maximum number of times the application layer will retry sending a response or
an unsolicited response to the master station. This does not include any retries performed by the data
link layer. Valid values are between 0 and 255.
Note: Using application layer Confirmation and Retries is inherently more efficient than
using data link layer Confirmation and Retries. Each fragment sent by the
Application layer may require as many as 10 data link layer frames to be sent, each
with its own confirmation message. The application layer is typically preferred for
message confirmation for this reason.
The Application Timeout is the expected time duration (in milliseconds) that the master station's
application layer requires to process and respond to a response from the SCADAPack controller.
This SCADAPack controller uses this value in setting its time-out interval for master station
responses. This value should be large enough to prevent response time-outs. The value must be kept
small enough so as not to degrade system throughput. The value of this element is dependent on the
master station. Valid values are between 100 and 60000 milliseconds.
The Time Synchronization section of the dialog defines when and how often the SCADAPack
outstation prompts the master station to synchronize the SCADAPack controller time. Messages
must be sent between the Master and Remote stations for Time Synchronization to work. Valid
selections for this parameter are:
 The None selection will cause the SCADAPack controller to never request Time
Synchronization.
 The At Start Up Only selection will cause the SCADAPack controller to request Time
Synchronization at startup only.
 The Interval selection will cause the SCADAPack controller to request Time Synchronization at
startup and then every Interval minutes after receiving a time synchronization from the master.
Valid entries for Interval are between 1 and 32767 minutes. The default value is 60 minutes.
Note: Time Synchronization may instead be initiated by the Master for each Outstation.
This may be selected in the Add/Edit Master Poll dialog. It is not required to enable
Time Synchronization at both the Master and the Outstation.
The Unsolicited Response section of the dialog defines which class objects are enabled or disabled
from generating report by exception responses. Unsolicited responses are individually configured for
Class 1, Class 2, and Class 3 data.
The Enable Unsolicited controls enables or disables the generation of unsolicited events for Class 1,
Class 2 or Class 3 data. If unsolicited responses are disabled for a Class the controller never